Lecture Notes on 30 July 2014

# merges two sorted lists
def merge (a, b):
  c = []
  idxA = 0
  idxB = 0

  while ((idxA < len(a)) and (idxB < len(b))):
    if (a[idxA] < b[idxB]):
      c.append (a[idxA])
      idxA += 1
    else:
      c.append (b[idxB])
      idxB += 1

  while (idxA < len(a)):
    c.append (a[idxA])
    idxA += 1

  while (idxB < len(b)):
    c.append (b[idxB])
    idxB += 1

  return c

# binary search in a sorted list
def binary_search (a, x):
  lo = 0
  hi = len(a) - 1
  while (lo <= hi):
    mid = (lo + hi ) // 2
    if (x < a[mid]):
      hi = mid - 1
    elif (x > a[mid]):
      lo = mid + 1
    else:
      return mid
  return -1

# sequential search in an unsorted list
def seq_search (a, x):
  for i in range (len(a)):
    if (x == a[i]):
      return i
  return -1

def seq_search2 (a, x):
  index = []
  for i in range (len(a)):
    if (x == a[i]):
      index.append (i)
  return index

# selection sort in place
def selection_sort (a):
  for i in range (len(a) - 1):
    min = a[i]
    min_idx = i
    # find the minimum
    for j in range (i + 1, len(a)):
      if (a[j] < min):
        min = a[j]
        min_idx = j
    # swap the elements
    a[i], a[min_idx] = a[min_idx], a[i]

def main ():
  a = [9, 1, 8, 2, 3, 7, 5, 6, 4]
  print (a)

  selection_sort (a)
  print (a)

main()